At the time, Columbine was the deadliest school shooting in modern U.S. history, but it has since been surpassed by the Feb. 14 mass shooting at Marjory Stoneman Douglas High School, in Parkland, Florida, which killed 17 people.

After the Parkland massacre, survivors organized a national action with a similar name: Enough! National School Walkout, which took place on March 14, a month after the shooting.

19 years ago today, these 13 people were killed at #Columbine High School in Colorado.

Unlike that walkout, where students left their classes for 17 minutes to commemorate the 17 Parkland victims, participants in Friday’s event left school for the day and will not return.

Although organizers of today’s protest weren’t alive during the Columbine tragedy, they see the shooting as a grim pivotal event that ushered in the epidemic of shootings across the country — and they are determined to put a stop to them.

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“We can rise up together and declare, with one ringing voice, that the age of national indifference towards the ever-growing death toll is over. We can change America forever, all before we reach 20 years of age.”

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“Keeping up the momentum is important,” Connecticut sophomore Lane Murdock, the student who conceived Friday’s walkout, told USA Today. “We saw that low after March for Our Lives” — the student-led series of demonstrations for gun violence prevention on March 24 — “but students aren’t quitting on this. Our generation is demanding change and won’t be ignored or swept under the rug.”

More than 2,600 National School Walkout events were planned around the country with tens of thousands of students expected to be involved, according to the event’s website.